The present invention relates to a touch panel device for detecting a touch thereon of a finger or an object such as pen, more specifically to a touch panel device wherein an interdigital transducer (hereinafter referred to as xe2x80x9cIDTxe2x80x9d) is used, for detecting a touched position by sensing an attenuation or break of surface acoustic wave (hereinafter referred to as xe2x80x9cSAWxe2x80x9d).
Along with the growing popularity of computer systems mainly represented by personal computers, devices for inputting new information or giving various instructions to a computer system by touching a finger or pen on a screen of a display device on which information is displayed by a computer system have come to be widely utilized. When inputting operation is executed by a touching method in response to information displayed on a screen of a display device of a personal computer etc., a touched position (indicated position) has to be detected with a high accuracy.
Among touch panel devices for detecting a position touched by a finger or pen, those provided with resistance film and those in which ultrasonic wave is used are being popularly utilized. The former having a resistance film detects a change of partial ratio of voltage caused by a touch of an object on the resistance film. A device of this type has an advantage of low power consumption, but has a disadvantage in such aspects as response time, detection performance and durability.
On the other hand, a device in which ultrasonic wave is utilized propagates SAW on for instance a non-piezoelectric substrate, so that a position touched by an object is detected by sensing an attenuation of SAW caused by a touch of an object such as a pen on the non-piezoelectric substrate. The inventors of the present invention have been pursuing studies and development of a touch panel device, wherein IDT that can be formed in a batch by a photolithography technique is used as a transducer for exciting or receiving SAW. In the mentioned touch panel device, an element constituted by IDT and piezoelectric thin film is employed as an excitation element for exciting of SAW or a receiving element for receiving the propagated SAW.
FIG. 1 is a schematic drawing showing a configuration of a conventional touch panel device wherein IDTs are used in the mentioned manner. Referring to FIG. 1, reference numeral 60 stands for a rectangular non-piezoelectric substrate made of forinstance a glass material, and on one of the respective end portions of X-direction and Y-direction of non-piezoelectric substrate 60, a plurality of excitation elements 65 consisting of input IDT and piezoelectric thin film for exciting SAW are aligned in such a manner that each of them corresponds to each of a plurality of tracks. Also, on the other respective end portions of X-direction and Y-direction of non-piezoelectric substrate 60, a plurality of receiving elements 66 consisting of output IDT and piezoelectric thin film for receiving SAW are aligned so as to confront excitation elements 65.
In a touch panel device of FIG. 1, electric signals are inputted to each of excitation elements 65 to excite SAW so that SAW is propagated on the non-piezoelectric substrate 60, and each of receiving elements 66 receives the propagated SAW. And when an object touches on a propagating route of SAW on the non-piezoelectric substrate 60, SAW is attenuated. Therefore whether and a position where an object touched can be detected by sensing whether an attenuation of signal level received by the receiving elements 66 has taken place.
Also, the inventors of the invention offer a touch panel device wherein excitation elements and receiving elements are disposed so as to propagate SAW diagonally (along diagonal lines). FIG. 2 is a schematic drawing showing a configuration of electrodes of the mentioned touch panel device. Referring to FIG. 2, numeral 70 stands for a rectangular non-piezoelectric substrate made of for instance a glass material, and a central area surrounded by broken lines is a detecting region 70a where a touched position can be detected.
In the frame region outside of the detecting region 70a, which corresponds to the peripheral area of non-piezoelectric substrate 70, four IDTs 71 are placed. Each IDT 71 is provided with bus electrodes 72, 72 confronting each other and respectively comprising comb-like electrode fingers 73 that are bent halfway and alternately aligned. By such an arrangement, a row of comb-like electrode fingers 73 inclined in two directions from the confronting direction of bus electrodes 72, 72 is formed, which enables excitation of SAW in two directions and reception of SAW from two directions. In this example, IDTs 71 on the upper and lower sides are functioning as excitation elements for exciting SAW in two different directions at a time, while IDTs 71 on the left and right sides as receiving elements for receiving SAW from two different directions.
On the upper and lower sides, terminals 74, 74 for inputting and grounding connected to bus electrodes 72 of the respective IDTs 71 are provided. Also, terminals 74, 74 for outputting and grounding connected to bus electrodes 72 of the respective IDTs 71 are provided on the left and right sides. And to each of terminals 74, each of leading lines 77 is connected.
FIG. 3 is a schematic drawing of a flexible substrate 78 corresponding to FIG. 2. On the flexible substrate 78 a conductor pattern 79 is formed at a position corresponding to leading lines 77. And when such flexible substrate 78 is placed over a configuration of electrodes shown in FIG. 2, a touch panel device is constituted.
It is advantageous from a viewpoint of mounting process to utilize the flexible substrate 78 for drawing out signals from a touch panel device. As shown in FIGS. 2 and 3, IDTs 71 surrounded by long-sized bus electrodes 72 are disposed on the sides in the frame region closer to the detecting region 70a, around which leading lines 77 are disposed, and all leading lines 77 are united at one side. Leading lines 77 united in this way are connected to an exterior circuit through the conductor pattern 79 on the flexible substrate 78. Now, since the frame region is an area where a touched position cannot be detected, it is a critical factor for enhancing a product value to minimize the area of the frame region, and for such a purpose it is essential to narrow the width of bus electrodes 72 and leading lines 77.
In a conventional configuration as shown in FIGS. 2 and 3, a problem is that intensity of received SAW is lowered due to a resistance loss that is caused while a signal is transmitted through each of long-sized bus electrodes of IDTs placed all over the panel. In order to prevent such a resistance loss it is necessary to increase the width of bus electrodes and leading lines, which, however, is contradictory to the purpose of minimizing the area of the frame region. Meanwhile it might be another option to increase film thickness of the mentioned components, but in this case still a problem remains that production process will be more complicated, because the optimum condition of film thickness is different between excitation/reception unit (IDT) and transmission unit (bus electrodes and leading lines).
An object of the present invention is to provide a touch panel device wherein a resistance loss in a transmission unit can be minimized without enlarging a frame region.
Another object of the invention is to provide a touch panel device wherein the frame region can be further narrowed.
A touch panel device according to the first aspect of the invention comprises IDTs for exciting or receiving SAW placed on a peripheral area of a substrate, in which comb-like electrode fingers are aligned along bus electrodes confronting each other in a direction that is aligned with a direction from the center toward the periphery of the substrate, and at least one drawing electrode connected to the bus electrode positioned closer to the center of the substrate and led out to the peripheral area side of the substrate.
In the touch panel device of the first aspect, the drawing electrode is disposed from the bus electrode positioned closer to the center of the substrate to the peripheral area side of the substrate through inside of IDT. As a result, a signal will pass through the drawing electrode instead of being transmitted through long-sized bus electrodes one after another, therefore resistance loss in the bus electrodes is reduced.
The touch panel device according to the second aspect of the invention is the device of the first aspect, wherein IDT has a repeated constitution due to the segmentation by the drawing electrode.
In the touch panel device of the second aspect, IDT is evenly segmented into a plurality of regions by the drawing electrode. As a result, conversion efficiency of SAW excited at each side is leveled, therefore the conversion process can be simplified.
The touch panel device according to the third aspect of the invention is the device of the second aspect, wherein the drawing electrode is disposed so that impedance of each segmented region of IDT becomes equal.
In the touch panel device of the third aspect, impedance of each region of IDT segmented by the drawing electrodes is equal. As a result, excitation efficiency can be leveled.
The touch panel device according to the fourth aspect of the invention is the device of the third aspect, wherein electrostatic capacity of each segmented region of IDT is equal.
In the touch panel device of the fourth aspect, electrostatic capacity of each region of IDT segmented by the drawing electrode is equal. As a result, a stabilized drive detection can be performed.
The touch panel device according to the fifth aspect of the invention is the device of the third aspect, further comprising a plurality of drawing electrodes as in the third aspect, and resistance value of each of the plurality of drawing electrodes is equal.
In the touch panel device of the fifth aspect, resistance value of each of the plurality of drawing electrodes is equal. As a result, influence of resistance loss can be restrained within a certain level in each segmented region.
The touch panel device according to the sixth aspect of the invention is the device of any of the first to fifth aspects, wherein the width of the drawing electrode is (xe2x85x9c+n)xcex (xcex: wavelength of the SAW, n: an integer that is not negative).
In the touch panel device of the sixth aspect, the width of the drawing electrode is set as (xe2x85x9c+n)xcex (xcex: wavelength of the SAW, n: an integer that is not negative), therefore characteristic prediction can be made based on design parameters and a drop of excitation efficiency can be prevented.
The touch panel device according to the seventh aspect of the invention is the device of the sixth aspect, wherein the drawing electrode of the sixth aspect is of a metal strip array.
In the touch panel device of the seventh aspect, the drawing electrode is of a metal strip array. As a result, canceling effect of reflected wave can be expected also from the drawing electrode, and influence of unnecessary mechanical reflection that may occur in IDT can be alleviated.
The touch panel device according to the eighth aspect of the invention is the device of any of the first to seventh aspects, wherein at least one pad connected to the drawing electrode is provided within the bus electrode.
In the touch panel device of the eighth aspect, the pad connected to the drawing electrode is provided within the bus electrode. As a result, resistance can be reduced utilizing conductor unit of the bus electrode, and the frame region can be narrowed by omitting the area for the pad, besides influence of imperfect contact can be minimized thus resulting in an improved yield.
A touch panel device according to the ninth aspect of the invention comprises IDTs for exciting or receiving SAW placed on a peripheral area of a substrate, in which comb-like electrode fingers are aligned along bus electrodes confronting each other in a direction that is aligned with a direction from the center toward the periphery of the substrate; at least one drawing electrode connected to the bus electrode positioned closer to the center of the substrate and led out to the peripheral area side of the substrate; at least one pad placed in the drawing electrode; and a flexible substrate having at least one connection unit corresponding to the pad.
In the touch panel device of the ninth aspect, as in the first aspect, the drawing electrode is disposed from the bus electrode positioned closer to the center of the substrate to the peripheral area side of the substrate through inside of IDT, and a signal will pass through the drawing electrode instead of being transmitted through long-sized bus electrodes one after another, therefore resistance loss in the bus electrodes is reduced. In addition, the flexible substrate is placed. As a result, resistance loss can be further reduced and transmission can be stabilized.
The touch panel device according to the tenth aspect of the invention is the device of the ninth aspect, wherein the flexible substrate is disposed so as to cover the IDT.
In the touch panel device of the tenth aspect, the IDT is covered with the flexible substrate, which can also serve as a buffer member against an unexpected impact, resulting in a higher reliability.
The touch panel device according to the eleventh aspect of the invention is the device of the tenth aspect, wherein the flexible substrate has at least one leading line connected to the drawing electrode on a portion thereof covering the IDT.
In the touch panel device of the eleventh aspect, the leading line connected to the drawing electrode is disposed over the IDT. As a result, the frame region can be narrowed.
The touch panel device according to the twelfth aspect of the invention is the device of any of the ninth to eleventh aspects, wherein the flexible substrate is of a form folded in a direction of thickness of the substrate.
In the touch panel device of the twelfth aspect, the flexible substrate is of a form folded in a direction of thickness of the substrate on which the IDT is placed. As a result the leading line can be disposed along the folded portion, therefore the frame region can be further narrowed.
The touch panel device according to the thirteenth aspect of the invention is the device of the twelfth aspect, wherein the flexible substrate can be unfolded one-dimensionally.
In the touch panel device of the thirteenth aspect, the flexible substrate having a two-dimensional structure can be unfolded to a one-dimensional form. Therefore a mass production can be easily executed.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.